The present patent application is a Utility of Application No. PCT/NZ 2006/000268, filed Oct. 20, 2006.
This invention relates to a method and apparatus for sterilization. More particularly the invention relates to a method and apparatus for sterilization and vacuum packing without the requirement for a conventional pressure vessel or chamber.
Sterilization is an absolute necessity for various industries typically health care, laboratory, pharmaceutical and food processing industries. The most common and proven method used for sterilization is sterilization by pressurized high temperature steam in a pressure chamber or vessel for a prescribed period of time. Pressurized high temperature steam within a stainless steel pressure chamber is the preferred method for sterilization of laboratory equipment and in the industrial manufacturing sector.
It is necessary in hospital and health care environments, laboratory environments and in the pharmaceutical and food processing industry to either sterilize, autoclave, cook, pasteurize or retort various devices, instruments, material and/or products with pressurized high temperature steam or by means of a low temperature medium (e.g. ethylene oxide or equivalent low temperature sterilant) in a pressure vessel.
Various types of sterilization pressure vessels and autoclave chambers are historically utilized to sterilize such objects, items or products (hereinafter “items”). In all instances the sterilant must make contact with the surface of the or each item to be sterilized in order to enable sterilization to occur.
For moist heat sterilization using steam as the sterilant, it is essential that all surfaces of the items requiring sterilization are subjected to saturated steam at a predetermined temperature and pressure, for a predetermined period of time. Proper steam penetration requires adequate air removal.
In the medical environment, it is necessary that all medical items (equipment and materials) utilized for the treatment of patients are inherently safe for use so that the chance of spreading diseases is kept as low as possible. Hospital acquired infection is clearly the last thing either a patient or the hospital wants.
At the end of a correct sterilization process, items inside the sterilization chamber are sterile. The challenge to sterilizer manufacturers has been the variety of loads and varied manner of loading both in respect of how items are loaded and positioned in the chamber and how the load may be packaged. The load therefore has a direct impact on the relative efficacy of each method of removing air from the chamber and the load and is still a matter under debate.
The European standards (EN 13060 and EN 285—MDA SN 2001 [34]) have established several test methods that demonstrate the ability of a selected sterilization cycle to effectively remove air from hollow or cannulated devices and its ability to process porous items, such as packaged trays or drapes.
The problem therefore is that a sterilizer operator must make sure that the sterilizer and sterilization cycle selected for use is suitable for the intended purpose. Due to these complexities the EN 867 standard was introduced which describes specific non-biological indicator systems and process challenge devices for use in performance testing of sterilizers.
An unavoidable problem that faces sterilization practitioners is that the air in the room where the sterilizer is installed contains dust particles, which may carry micro-organisms. Accordingly, when the sterile load is taken out of the sterilizer, it may soon be contaminated again. Additionally sterile goods may be stored for quite some time before they are used. Moreover, they are transported through the hospital to the place they are to be used. It thus is obvious, that, when not protected, the items may most likely be re-contaminated by the time they are used.
Consequently the items must be put in packaging to prevent recontamination after sterilization. To minimize recontamination and augment the logistics and materials handling expediency of the sterilization process, the item(s) are usually prepackaged. The packaging heretofore typically include muslin wraps, various paper wraps and non-woven wraps, laminated film pouches and sterilization containers.
Sterile services technicians must have an understanding of how to properly select and apply the correct wrappers for the sterilization method chosen. The manufacturer and distributors must be able to provide detailed specifications regarding the properties of the product as well as documentation of acceptable results of its past performances. Improper selection of materials and packaging application can and will impede the sterilizing process.
Technicians are also responsible for quality assurance issues. They must assemble each package with care, being observant not to tear or damage the wrapper.
Each package is uniquely organized, depending upon content, to promote the sterilization process. Special attention must also be given to how the sterilizer is loaded.
When using the various types of wraps, medical instruments are placed in a tray, wrapped by a recommended procedure, taped, labelled and placed in a steam or low temperature sterilizer. During sterilization the packaging must allow air to be removed and steam or low temperature medium to penetrate the packaging and kill any bacteria. After sterilization the packaging must enable the condensate back out and should provide an effective microbial barrier for immediate use of the sterile items.
Disadvantages in the use of the sterilization wraps include the limited shelf life of the wrapped instruments, the porous nature of the wrap, the likelihood of retaining moisture, the fact that the wraps are not easily stackable and potential punctures of wrapping materials thereby causing contamination. In addition the wrapping of packs necessitates a certain skill set and requires a high labour content due to the multilayer barrier construction and requires specially trained staff to undertake the work.
It is essential that a packaging system with its content meet the requirements in terms of sterility maintenance and protection of its contents. That is why any packaging should be validated in combination with the actual load and the sterilization process used.
Various sterilization containers have been heretofore proposed which provide a hermetically sealed container with various filters which provide a relatively long shelf life, which cannot be easily punctured, which enable improved organization of the medical instruments and which are stackable. Sterilization containers made of metal such as stainless steel and aluminum are used, but are expensive. These devices are generally also opaque, thereby preventing a visual inventory of the container interiors.
Consequently, sterilization containers made of plastics have been developed. These are constructed to withstand the harsh environments of the sterilization chamber and are clear such that inventories of the containers can be seen through the container. The containers, however, are relatively expensive and still require to be put through the sterilization pressure chamber.